The present invention relates to communications between a host and a storage device, and more particularly to a completion notification of processing transmitted from the storage device to the host.
Devices using various types of media such as optical disks and magnetic tapes are known as storage devices. Among them, hard disk drives (hereinafter referred to as “HDD”) have become popular as storage devices for computers to such an extent that they are one of the storage devices indispensable for today's computer systems. Further, not limited to computers, their application is widening more and more because of the superior characteristics with the advent of moving picture recording/reproducing devices, car navigation systems, portable terminals, and removable memories for digital cameras and so on.
A magnetic disk used in the HDD has a plurality of tracks that are concentrically formed. Each track is divided into a plurality of sectors. Address information of a sector, and user data, are written to each sector. Accessing a desired sector by a head element according to the address information of the sector makes it possible to write data to the sector or to read data from the sector. A signal read out from a magnetic disk by the head element through data read processing is subjected to waveform shaping, decoding processing and other prescribed signal processing by a signal processing circuit before the signal is transmitted to a host. Data transmitted from the host is also subjected to prescribed processing by the signal processing circuit in like manner before the data is written to the magnetic disk.
As an interface used for data transmission between the host and the HDD, protocols such as the SCSI protocol and the ATA protocol are in general used. In particular, the ATA protocol is used in many computers with the object of improving interface functions and achieving low cost. In addition, the ATA protocol is broadly used also as interfaces of other types of storage devices such as optical disk storage devices.
As far as the ATA protocol is concerned, a HDD is provided with a function of notifying a host of the completion of input-output (I/O) processing of write and read as user data input-output processing. The host may set this function ON or OFF at the time of starting the HDD. If this function is brought into an ON state, the HDD transmits to the host a completion notification of I/O processing every time I/O processing is completed. Incidentally, as for the completion notification of I/O processing, patent document 1 (Japanese Patent Application Laid-Open No. 2001-312373) discloses the technology for improving the performance of a HDD, for example, by controlling the issuance of a command complete signal to a command.